E85 or 91 for car not driven a lot
 

my BRZ will strictly be my weekend car, most likely i will only drive the car about 20 miles per week. i have flex fuel kit installed and i love to run E85 whenever's possible. but since now the car's going to sit in the garage for long stretch of time between being driven, which fuel is better for the gas tank when car is parked? or it does not matter at all.

You live in cali, i will not worried about that

Pretty sure E85 will be absorbing moisture as it sits, I think 91 is a safer bet here.

you have the kit, put e85 in it but not a full tank.

unless you in the habbit of leaving your fuel cap off, it wont be a problem.

modern fuel tanks are sealed systems, so no moisture to absorb.

Keep fuel cap on, and your E85 storage containers sealed and you can store it for months like normal petrol.

been full time E85 for 5 years , fill tank and 4 by 20 litre jerry cans , lasts me over a month, no problems

While I believe you, as a previous AAA driver, people constantly had issues with moisture freezing on really cold days. Plugging bad fuel filters or whatever, it was a job for Isopropyl alcohol. This is in Vermont, I doubt they'd see swing in temperatures like we do (some days will go from 20 above down to 15-20 below freezing overnight)

I'm in Normal and my BRZ is my weekend only car running E85 as often as I can. Ive had the car sit for a good two weeks one time and it ran and started just fine.

Your in socal, store it for decades, you'll be fine no matter what fuel.

If you had small amounts of water in E85 it would just mix in, so im a little confused how the moisture would freeze. When we used to get water in petrol tanks we would add a couple of litres of alcohol as it mixed with water and petrol.

Was this problem in older cars that didnt have sealed fuel tank systems ?

Not so much in the tank, but the moisture in the filter froze and wouldn't let gas pass. Early 2000s and 90s cars are what I'm referencing. Again, Isopropyl would fix anything mixing in the tank. I still think straight up gasoline is better for a car that sits

12 mpg (driving like a nut on E85) * 12 gallons (full tank) = 144 miles minimum to empty tank. At 20 miles per week, thats 7 weeks of fuel sitting in the car. Maybe just fill up half when you do so you don't have old E85 sitting in the tank so long.

yeah, good thinking